DIY Bench Supply
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Project Summary This project started as me trying to fulfil a need for a reliable and convenient power supply and wanting to learn some lessons along the way. I designed the project in sketchup and then proceeded to go through various stages of construction. There were a few design changes along the way but nothing major. I decided to add an external voltage probe and a switch to allow voltage measurements either from the ammeter or ground. Posts Archive: Power Supply Design Lessons Learnt: As my first project i have learnt a lot and would certainly do things differently in future. Aluminium bending is easier than i expected but getting a good finish is difficult. Brushing of aluminium must be done first then the piece must be kept scratch free. Its also very important to allow room for cabling. I assumed that the wires would all be flexible enough that i could just put them where i needed them but the need to make them quite long (in order to fix them in easily) combined with the quantity of wires in this supply meant that i could barely get the thing closed at the end. Future Modifications: Desk Lamp – The power resistor is effectively wasting energy and i would like to replace it with something slightly more functional. I have some cheap power LEDs that i bought on ebay and one of these should draw enough power to be able to replace the power LED. I plan on buying a goose-neck lamp, modifying it with an LED and attaching it to the side of the power supply. Side Grills – The original design had perforated aluminium to act as side vents on the case. I haven’t put these in yet but plan on doing in the near future. These are purely aesthetic. Version 2 – Thanks to all the comment on hackaday I’ve already got ideas forming for a 2nd version. I like the idea of modifying the PSU circuit to give a higher output (~48v) and then using various regulators for the outputs i need. I also want to come up with a current limiter, but i’m not sure of how to do this. If anyone has ideas then please leave a comment. Kit version – I did consider this in the first place but comments have got me thinking again. It would be good to make this into a kit that simply bolts on to a standard PSU. The design would have to change a bit to acomodate the standard ATX screw hole locations but i’m sure i’m up to the task. |
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TG's Electronic exploration 
That is a very nice design! I like it a lot!
Keep up the great work!
Way better than mine, all I did was bodge some connectors onto the end of leads and have done, and I thought a toggle switch was going too far 🙂
A kit of electronic parts to be added to an ATX psu would be great. In my case I amsearchingfor something like this.
Regards
I am thinking of making a few kits when i’ve done a couple more projects. It will probably be a long while from now though
I agree with SEGU, if you make a kit I’d buy one. 🙂
A suggestion for current limiting would be to use a transitor stage betweeen your output now and the new, limited output like : http://www.zen22142.zen.co.uk/ronj/add-on.html
though I would maybe suggest the TIP31BG from onSemi , which is slightly beefier than the original BDE
Kick butt design!! I’ve hacked a couple old supplies myself, but nothing like this. One to charge RC car batteries, one for general purpose, and one to feed a more complicated power supply. They just go to connectors or terminal blocks. This one is similar to my “more complicated”, just lower voltage and current. For your first project you did an awesome job!! It seems you learned some of the same things I did with my first projects. Keep up the great design work and I look forward to seeing more!
I used the poly fuses (resetable) for the outputs – not variable but it gives you some (fixed) protection from shorts. I got several values (100, 200ma and a 5a) from digikey. Sparkfun also has some.
I have read and article on adding a variable resistor in the voltage regulator feedback circuit to get a variable output from the supply. My question would be that you would have to do this for each rail. Would this be the case or is there one regulater with taps for each voltage?
Do you have a link to the article? I have read similar stuff before but have always been unsure of exactly what is required. My guess is that it would depend on the power supply in question. All i did here is add my own linear regulators to the output of the supply.
This unique posting, “DIY Bench Supply TG’s Electronic exploration” was great. I am printing out a clone to demonstrate to my buddies. I appreciate it-Juliann
Great article! There are several ways to go for overcurrent protection depending on how much output current you are trying to achieve. I recommended adding a series FET with a floating gate driver, like an LT1910 to your output – this would provide short circiut protection.
For lower current protection, you could use a current shunt amplifier (off of the same shunt you had on the 1910), like an INA169, to feed current level back to an A/D pin on your microcontroller. You could use this threshold to trip the LT1910 off.
If you want more of a linear current limit, like on lab power supplies, you need to configure the output as a current source. This could use a power BJT/OPAMP current source. You would attach a BJT in series with your output, and add a series current shunt from emitter to load. You could drive feedback from the shunt to the opamp to adjust the base current, thereby adjusting Ice.
Be aware that anytime you do this, you are dropping voltage across your pass transistor, which is dissipating power in that device (Ploss=Vdrop*I). A TO-220 device has approximately 2W thermal limit in open air, exhibiting 40C/watt temperature rise. You would need adequate heatsinking for this approach.
An LM350 can be configured as a current limiter very easily. Take a look at the (TI version of the) datasheet. There is a schematic in the application examples section. One or two resistors and you are done.
This is a great job! I like the construction and on how you built it. For other reference about power supply you may check Panther.ph Again, what an amazing job!
Would you consider selling everything but the actual PSU that I could hook to my own PSU?
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” i need. I also want to come up with a current limiter, but i’m not sure of how to do this. If anyone has ideas then please leave a comment.”
Do you mean, Current REGULATOR? If so, see this…
https://en.wikipedia.org/wiki/LM317
I think every electronic experimenter has collected a couple of these power supplies and expected to do this – but I think in the history of mankind, you are the first to get around to doing it and you made the rest of us look bad by doing such a professional job 🙂
Very nice ckt ideas hope to receive e mails which will improve me
Veľmi sa mi páči prevedenie toho zdroja.